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Biomedical subjects

K Soma

Publications and source records attributed to K Soma.

At least 91 records · Page 5Linked to original sources
PubMed1993

Social regulation of the brain-pituitary-gonadal axis.

Reproduction in vertebrates is regulated by the hypothalamic-pituitary-gonadal axis via neural and hormonal feedback. This axis is also subject to exogenous influences, particularly social signals. In the African cichlid fish Haplochromis burtoni, gonadal development in males is socially regulated. A small fraction of the males, which are brightly colored, maintain territories and aggressively dominate inconspicuously colored nonterritorial males. Here we show through manipulation of the social and endocrine environment that changes in social status and gonadal state are accompanied by soma size changes in a population of gonadotropin-releasing hormone-containing neurons in the ventral forebrain. In territorial males, these cells are significantly larger than in nonterritorial males. When an animal switches from being territorial to nonterritorial through a change in social situation, these cells shrink; in animals that change from nonterritorial to territorial status, the cells enlarge. These gonadotropin-releasing hormone-containing cells project to the pituitary and are ultimately responsible for regulating gonadal growth. This mechanism of socially induced cell size change provides the potential for relatively quick adaptive changes in the neuron-endocrine system without nerve cell addition or death. Since the structure of this regulatory axis is conserved among all vertebrates, other species with socially modulated reproductive physiology may exhibit a similar form of physiological regulation.

Animals↗
PubMed1993

Lysosome labilizers potentiate the antitumor effects of tumor necrosis factor-alpha.

Enhancement of in vitro cytotoxic activity of tumor necrosis factor-alpha (TNF-alpha) was observed in combination with lysosome labilizers, particularly with urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and lipoprotein lipase (LPL). The concentration of TNF-alpha resulting in 50% cytotoxicity to L929 cells was only 20-30% of the value for TNF-alpha alone, when used in combination with a nontoxic dose of u-PA, t-PA or LPL. Furthermore, combined intravenous (i.v.) administration of TNF-alpha (3.5 x 10(5) U/mouse) and u-PA (300 IU/mouse) markedly increased the in vivo antitumor activity of TNF-alpha to Meth A tumors transplanted into BALB/c mice; the tumor weight in co-administered mice was about 40% of that in mice given TNF-alpha alone on day 6. The combination therapy of TNF-alpha (7.0 x 10(4) U/mouse, i.v.) and u-PA (300 IU/mouse, i.v.) was also effective for L929 tumors in Crj:CD-1(1CR)-nu nude mice compared with the conventional therapy with TNF-alpha alone. These results suggest that the combination of TNF-alpha and lysosome labilizers is a promising antitumor therapeutic regimen with clinical potential.

Animals↗
PubMed1993

Stress of tooth and PDL structure created by bite force.

Stress is created by the bite force and distributed along the tooth towards the PDL structure. It is of interest to investigate the complex tooth structure, consisting of enamel, dentine, pulp, and thin cementum layer and how it functions in stress distribution. This study was intended to analyze the role of the tooth and PDL structures in stress distribution, by using a three-dimensional finite element method. A mandibular first molar was constructed for the finite element model. The bite forces were measured by Pressensor, and these bite force values were programmed to load down upon the occlusal surface of the model. The results were expressed by stress contours and principal stress graphs. The stress was found to decrease as it distributed from the occlusal surface towards the cervical portion in the dentine and the pulp. In contrast, the stress, especially a compressive stress, increased gradually in the enamel layer in the lower half of the crown, in the same direction. It was apparent in displayed pattern of stress that the stress distributed outward towards the surrounding portion of the lower half of the crown. This resulted in a uniform magnitude of the principal stresses for all aspects of the mesial and distal roots. The stresses of both roots were generally compressive stress. When comparing the stress values of sampling points positioned between the root surfaces and the periphery of the PDL (the alveolar wall), all principal stresses for those of the PDL (periodontal ligament) were less than those of the root surfaces. These findings revealed that the PDL, the dentine, and the pulp functioned in cooperation in stress reduction; and the sequences of enamel, dentine, and pulp influenced the pattern of stress distribution. The different material properties of the tooth structure in sequence was considered a very important factor for stress reduction and for the pattern of stress distribution, especially in the root.

Alveolar Process↗
PubMed1993

[Aniline-induced methemoglobinemia monitored by pulse oximetry].

A case of aniline-induced methemoglobinemia is reported. When the pulse oximeter reading (SpO2) was 80%, the oxygen saturation measured by a co-oximeter (SaO2) was 61.2%, the oxygen saturation calculated from PaO2 values was 98.9% and methemoglobin level was 38.8%. After methylene blue injection, methemoglobin level decreased gradually. With a decrease of methemoglobin level, SpO2 approached SaO2. If disparity between SpO2 and the oxygen saturation calculated from PaO2 values is noted, the presence of methemoglobinemia must be suspected. In clinical situations, the pulse oximeter permits the continuous noninvasive monitoring of oxygen saturation. It is necessary, however, to consider the potential errors in pulse oximetry.

Adult↗
PubMed1993

[The etiology of sudden cardiopulmonary arrest in subarachnoid hemorrhage].

Sudden death due to subarachnoid hemorrhage (SAH) is not uncommon. However, the mechanism remains unclear. In this paper, sixty-eight consecutive patients with sudden death in SAH (DOA group) were studied to clarify the etiology of sudden cardiopulmonary arrest (CPA) in SAH. SAH was confirmed by CT scan and/or by autopsy. These patients accounted for 10% of the total intrinsic DOA patients in that period. Clinical symptoms, CT scan and autopsy findings concerning the DOA group were carefully evaluated and compared to those of patients with SAH of WFNS Grade V (V group). The DOA group accounted for 10% of all SAH patients. Average time interval from the onset of SAH to the recognition of CPA was 21.2 minutes. In 30% of cases, the time interval was within 15 minutes. Pulmonary edema was recognized as being significantly higher in the DOA group than in the V group (P < 0.01). In CT finding, the number of patients who were classified into S type (mainly subarachnoid clot only) was significantly higher in the DOA group than in the V group (P < 0.01). The CT Score and MAX. CT NO. in the DOA group were significantly lower than in the V group (P < 0.01 and P < 0.0001, respectively), suggesting that the intensity of subarachnoid hemorrhage was not severe in the DOA group. Postmortem histological examination of the myocardium was carried out on 6 cases of the DOA group. A contraction band necrosis in the myocardium which did not correspond to the coronary perfusion area was found in all 6 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[High accuracy measuring device for dental cast--using device with flat laser beam].

A new system has been developed for measuring the surface morphology of the occlusal material. The main characteristic of the system is utilizing a flat laser beam to produce high accuracy measuring and to enable measuring 200 points at the same time on a line of 30 mm in length. It takes 8 to 10 minutes to digitize the whole morphology of a dental cast. The system has a central processing unit that assembles a series of digitized points into a data file of the dental morphology. It is also able to recognize the graphical image of the numerically reconstructed morphology on the CRT. Application of this measuring system enables the approach to the qualitative and quantitative evaluation of the spatial relationship between the opposing teeth at near the occlusal contact.

Dental Casting Technique↗
PubMed1992

[A dental anthropological study of Chinese in Taiwan (3). Dental trait].

Models of the upper and lower dental arches of 125 Chinese children in Taiwan with acceptable normal permanent dentition were surveyed in order to understand the developmental grades of dental traits from the viewpoint of dental anthropology. Developmental grades of dental traits were classified, calculated, statistically analysed by x2 test and results were summarized. Upper anterior teeth showed high frequency of shovel form; upper lateral incisors showed less tendency of regression. Interstitial cusp, lingual cusp, paracusp, central prominence and occlusal groove of lower premolars developed prominently. Upper molars showed low frequency of Carabelli cusps. Hypocone of upper second molars showed strong tendency of regression, but metacone had low regression tendency and a strong degree of compression. Compared to Japanese, Central American and South American Indians and Caucasians, the development of dental traits of Chinese in Taiwan was more similar to that of Japanese than to others. The characteristics of dental trait of Chinese in Taiwan and Japanese also showed greater similarity to Central and South American Indians than to Caucasians.

Anthropology, Physical↗
PubMed1991

[Genetic and environmental characteristics in dento-craniofacial morphology--using materials from survey on Latin American Indians].

Most previous researches of hereditary characteristics of the craniofacial skeleton have used the twin-study method. In this study, dental anthropological materials were used to clarify genetic and environmental characteristics of the dento-craniofacial morphology. The sample consisted of four groups including Mexican Indians (N = 71), Peruvian Indians (N = 41) and their ancient ancestors: skulls of Mexican Indians (N = 33) and Peruvian Indians (N = 34). These groups shared the common origin of the Mongoloid race. Morphological similarity and difference among these groups were examined by principal component analysis and Student t-test using the dento-craniofacial data based on roentgenographic cephalograms and dental casts. The morphological similarity means the genetic characteristics which maintained during time differences between ancient and present times and throughout regional differences between Mexico and Peru. The morphological difference means the environmental characteristics which produced during the time differences and throughout the regional differences. Results were as follows: (1) The genetic morphological characteristics were found predominantly in the anterior cranial base, the dental arch form and to a certain extent in the basal portion of the mandible and the vertical dimension of the naso-maxillary complex. (2) The environmental characteristics were found predominantly in the muscular portion of the mandible, the alveolar portions of the maxilla and the mandible, the length of the dental arch and to a certain extent in the antero-posterior dimension of the maxilla.

Adult↗
PubMed1991

[Dental anthropological study of Mongoloid in China].

The purpose of this study was to evaluate the craniofacial and occlusal characteristics of the inhabitants in China. The material consisted of cephalograms, pantomograms, dental casts and anthropological measurements taken from 517 inhabitants: 416 Han Chinese in Beijing, Shanghai, Guangzhou and Changchun and 101 Mongolians in Hohhot. The data were compared among the above five regions and also with the Japanese data. The findings were summarized as follows: I. Craniofacial characteristics; a) The Han Chinese and the Mongolians showed brachycephaly. b) The inhabitants in Guangzhou showed a tendency of bimaxillary protrusion with a smaller facial height, and the inhabitants in Changchun showed a larger gonial angle with a larger facial height than those of the other regions. c) The Mongolians had a larger value of the saddle angle and of the bi-gonial breadth. d) Compared with the Japanese, their craniofacial complex was characterized by a larger facial angle, smaller mandibular plane angle and a smaller gonial angle. II. Occlusal characteristics; a) The inhabitants in China had a similar tendency in the dental arch form and in the dental trait frequency. b) The inhabitants in Beijing had a larger mesiodistal crown-diameter of the anterior teeth than those in the other regions. c) Compared with the Japanese, their teeth were characterized by a smaller mesiodistal crown-diameter (especially on the upper first molar), higher frequency of shovel-shape and lower frequency of Carabelli's tuberculum.

Adolescent↗
PubMed1991

[A dental anthropological study of Chinese in Taiwan. I). Craniofacial morphology].

The cephalometric films were collected from 30 boys and 30 girls of 12 years of age, and from 36 males and 34 females of 18 years of age; all of whom were Chinese in Taiwan, all possessed acceptable occlusion to survey the craniofacial morphology and characteristics associated with dental anthropology. Data were analysed by the computer program at the Department of Orthodontics of Japan Tokyo Medical and Dental University. Data were compared with Japanese, North American Caucasians, Central and South American Indians from papers. It was concluded that: 1) Chinese in Taiwan were similar to Japanese, Central and South American Indians, in that; all possessed a shorter frontal cranial base and depth of face, and were completely different from North American Caucasians. The direction of growth showed counter-clockwise rotation in the four Mongoloid races; however, Caucasians showed straight--down growth. The four Mongoloid races had more frontal position of A,B point and more labial inclination of anterior tooth axis than Caucasians. 2) Chinese in Taiwan were similar to Japanese, but were different from Central and South American Indians, in having a flatter infraorbital outline, longer facial height, flattened mandibular plane angle and a more frontal position of chin. 3) Chinese in Taiwan were characteristically different from Japanese by having a smaller interincisal angle, lower frontal facial height, mandibular angle and mandibular plane angle. In summary, the results indicated that Chinese in Taiwan are characterized by having a wide but short face pattern, a retroposition of the mandible ramus, a more upright mandible angle and a prominent labial inclination of anterior tooth axis.

Adolescent↗
PubMed1991

[A dental anthropological study of Chinese in Taiwan (2). Teeth size, dental arch dimensions and forms].

Both upper and lower dental study models were collected from 30 boys (12 years old) and 30 girls (12 years old) with acceptable normal occlusion to understand the characteristics of the crown size, dental arch width and length such as (1) mesiodistal diameters of crown size from central incisor to first molar, (2) the width and length of dental arch and basal arch and (3) the morphology of dental arch form. After statistical analysis, data were compared with Japanese, Central and South American Indians and North American Caucasians from papers. The results were: (1) There was no statistical difference in teeth size between males and females, except the upper first molar of males was larger than that of females, lower central incisor of males was smaller than that of females. (2) The dimensions of dental arch of males were larger than that of females in general, especially such items as width and length of basal arch. (3) The crown size of Chinese male was in generally smaller than that of four other races, especially the upper canine, lower central incisor and first molar. The crown size of Chinese females showed that although the lower first molar was smaller than that of Central and South American Indians, but the upper first premolar, lower canine and central incisor were larger than that of Japanese. Upper lateral incisor was larger than that of South American Indians. Compared to that of North American Caucasians, Chinese females had a smaller upper central incisor and a larger upper first premolar. (4) The dimensions of dental arch in Chinese were very similar to Japanese, South and Central American Indians, but wider and shorter than Central and South American Indians. (5) The superimposition of dental arch form showed that the four races of Mongoloids had similar ovoid dental arch forms.

Asian People↗
PubMed1991

Three-dimensional digitization: method for evaluating morphological differences between teeth.

A new comparative method has been developed for evaluating morphological differences between a pair of teeth. This method consists of five steps: 1) digitization of the surface morphology of the teeth, 2) standardization to enable comparison of the teeth on a common axis, 3) reversal of data on one tooth to enable comparison with the opposite tooth, 4) qualitative evaluation by computer graphic superimposition and 5) quantitative evaluation by the set operation. To illustrate its effectiveness, this method was applied to a pair of extracted premolars. Application to the dental crown on a clinical plaster cast was also discussed.

Bicuspid↗
PubMed1989

[Study on distribution form of mesiodistal crown diameter in large sample: Part II].

The purpose of this research was to examine the distribution of the tooth size in a large sample. The objective teeth were the left upper and lower fourteen teeth except the third molar. The tooth size of 1,000 dental casts from the Japanese female orthodontic patients was measured. On each of them, a histogram and a set of statistics (mean, standard deviation, coefficient of variation, skewness, kurtosis, Geary value) are given in order to examine the distribution. The findings are as follows: 1) Each tooth may be classified into the following four types of distribution except the congenitally missing data. TYPE I: A normal distribution was observed in the upper and lower central incisors, the lower lateral incisor, the lower canine, the upper and lower first premolars, the upper second premolar, the upper and lower first molars and the lower second molar. TYPE II: A positively skewed distribution was observed in the lower second premolar. TYPE III: A negatively skewed and leptokurtic distribution was observed in the upper canine and the upper second molar. TYPE IV: An extremely negatively skewed and leptokurtic distribution was observed in upper lateral incisor. 2) With the four teeth which were classified into TYPE II, TYPE III and TYPE IV, the distribution of the lower second premolar was concluded to be of normal distribution by logarithmic transformation. The distribution of the upper canine and the upper second molar was judged to be of lognormal distribution and the upper lateral incisor also was judged to be of three parameter lognormal distribution and four parameter lognormal distribution. 3) The distribution of thirteen teeth except the upper lateral incisor was judged to be of normal distribution, by considering the congenitally missing data and the outlier in statistical data of the tooth.

Asian People↗